Packaging pouches are typically made on vertical form, fill and seal machines. Using such a machine, a flat web of synthetic thermoplastic film is unwound from a roll and formed into a continuous tube in a tube forming operation, by sealing the longitudinal edges of the film together to form a lap seal or a fin seal. The tube thus formed is pulled vertically downwards to a filling station. The tube is then collapsed across a transverse cross-section of the tube, the position of the cross-section being at a sealing device below the filling station. A transverse heat seal is made by the sealing device at the collapsed portion of the tube, thus making an airtight seal across the tube. The sealing device generally comprises a pair of jaws. Conventional sealing devices used for this application are of impulse heat sealing type and are sold under the trade-mark ROPEX.
After making the transverse seal, but before the jaws of the sealing device are opened, a quantity of material to be packaged, for example a liquid is caused to enter the tube at the filling station, and to fill the tube upwardly from the aforementioned transverse seal. The tube is then caused to move downwardly a predetermined distance. This movement may be under the influence of the weight of the material in the tube, or it may be caused by pulling or mechanically driving the tube. The jaws of the sealing device are closed again, thus collapsing the tube at a second transverse section. The second transverse section may be above, usually just above the air/material interface in the tube, or the second transverse section may be below the air/material interface. In these machines, the sealing device seals and severs the tube transversely at the second transverse section. The material filled portion of the tube is now in the form of a pillow shaped pouch. Thus the sealing device has sealed the top of the filled pouch and sealed the bottom of the next to be formed pouch, all in one operation. The filling of the product may be conducted on a continuous or intermittent basis. One such vertical form, fill and seal machine of the type described above is sold under the trade-mark PREPAC. Other suitable machines are sold under the trade-marks INPACO and ELECSTER.
A variety of flowable materials may be packaged in this manner, for example, milk, syrups, sauces, juices, water and the like. The term “flowable material” is meant to encompass materials which are flowable under gravity or may be pumped. Such materials may include emulsions, pastes, peanut butter, preserves, dough, ground meat, powders, detergents, oils and granular solids. It is anticipated that the pouches could be used for containing flowable materials, in particular foods that are packaged under sterile, pasteurized or aseptic conditions.
The pouches produced through this type of process can be manufactured to contain any volume of flowable material. In the situation where drinking fluids are packaged in this fashion, a typical size might be 250 mls or 500 mls. In such instance, it is possible to consume the fluid directly from the pouch.
In some circumstances, it is desirable that such pouches be produced as strings of a plurality of sealed pouches connected together and that they be easily separable in order to be sold individually. In this case it is essential that the pouches in the strings be easily separated without the potential of tearing open the adjacent pouches. There are several references that disclose machines that are directed towards producing strings of pouches that can be separated by tearing or rupturing a rupturable portion between adjacent pouches. For example, such machines are disclosed in U.S. Pat. No. 4,064,776, U.S. Patent Application Publication No. 2004/0231291 A1, PCT Patent Application No. WO 00/59784, European Patent Application No. 1 449 769 A1, European Patent Application No. 0 042 586 and UK Patent Application No. 2 350 597 A. These machines make use of sealing jaws that use heat to produce the seal between adjacent pouches, in conjunction with a separate cutting blade that physically cuts perforations in the vicinity of the seal produced by the sealing jaws in order to produce a rupturable portion between adjacent pouches.
There are several factors that must be considered when using a separate cutting blade to create the rupturable portion. Firstly, the complexity of the machine is significantly increased as additional moving parts are required to operate the blade and the operation of the blade must be properly coordinated with the other operations of the machine. Further, since film materials typically used to produce the pouches such as polyethylene are notably abrasive, the blade eventually gets dull and must be replaced or sharpened on a regular basis. Furthermore, in order to change the design of the pouches or rupturable portion produced, the cutting blade must be replaced. These factors lead to increased maintenance and downtime of the machine, and, can also entail health and safety concerns as the service personnel is required to handle the sharp cutting blades.
Another drawback of using a separate cutting blade is that since the perforations are preferably created in the vicinity of the heat sealed portion, the film is generally still warm and softened in this area following the heat sealing operation. The warm and softened film can foul the cutting blade and affect its performance. Consequently, the blade must be kept relatively clean and sharp in order to ensure proper cutting. One known method of addressing this problem is to use the cutting blade to perforate the film at a distance from the heat sealed portion. This allows the blade to perforate the film in an area where the film is cooler and also creates a suitable clearance between the blade and the pouch so as to reduce the risk of the pouch getting damaged by the cutting blade. Evidently, this requires a larger seal area to be formed and therefore increases film consumption. Another method is to allow a period of time to expire between the heat sealing operation and the cutting operation in order to allow the film to cool. However, this increases the cycle time of the filling machine.
Since, pouches are meant to be one-time use packages it is appropriate that the manner in which they are manufactured is as economical as possible, without sacrificing the basic packaging requirements for the materials in question. Therefore, there is a need for a device and method that can reliably produce strings of sealed pouches connected by a rupturable portion and filled with flowable material in a fast, consistent and economic manner.